In the dental therapy, in case where the tooth caries area is restored by a metal cast, the tooth cavity after cavity preparation is often temporarily sealed with a temporary sealing material. For the purpose of this temporary sealing, there are included prevention of a foreign matter from entry into the cavity, protection against a stimulation from the outside, prevention of a dentin surface from contamination, and preservation of the occlusal relation, during a period of time up to the completion of a metal cast. As characteristics which a temporary sealing material to be used for such purpose should have, those set forth below can be enumerated. That is, it has good sealing properties; it can be readily removed; it has a strength to a some extent; and its temporary sealing operation is simple. Examples of temporary sealing materials which are used at present include thermoplastic stoppings comprising guttapercha as a chief material, zinc oxide eugenol cements, hydraulic temporary sealing material, and resin-based temporary sealing materials.
Though the stoppings are a material with high safety and can be extremely easily removed, they require not only a heating operation for softening but also skill in filling into the cavity so that if they fail in a filling timing, their sealing properties become extremely worse. Though the zinc oxide eugenol cements are a material with superior sealing properties, since their cured products are brittle, the removal operation thereof are difficult. Also, even if very small amounts of the zinc oxide eugenol cements attach to and remain in teeth, at the time of impression taking with a silicone impression material, they likely cause a delay of curing of the silicone impression material. Though the hydraulic temporary sealing materials are in a form of one paste, are cured by the moisture in the oral cavity, and are superior in the operability at the time of filling due to the nature of one paste, likewise the zinc oxide eugenol cements, their cured products are brittle so that the removal operation thereof are difficult. Further, though the resin-based temporary sealing materials are good in the operability, the characteristics are different among products, and their cured products are in general hard and brittle so that they are inferior in the operability of removal. In this case, while there are products having improved operability of removal by imparting softness to a some extent, it can not be said that such products having thorough capability. In addition, in recent years, as a new sealing process, there has been employed a process in which for the purpose of coating and protecting a dentin surface after the cavity preparation, the dentin surface in the cavity is previously subjected to one-layer coating with a resin having high fluidity, and a temporary sealing material is filled therein thereby effecting the temporary sealing has been employed. However, in this temporary sealing process, resin-based temporary sealing materials can not be used, and in case where a resin-based temporary material is used, the applied resin is adhered to the temporary sealing material, whereby the temporary sealing material can be no longer removed.
As described above, the temporary sealing materials which are used at present are not a product fully meeting the above-described characteristics, i.e., it has good sealing properties; it can be readily removed; it has a strength to a some extent; and its temporary sealing operation is simple. Especially, it is the present state that many of the products are difficult with respect to the removal operation, while those which can be readily removed are poor in the sealing properties.